Many mechanical systems have rotating members that perform functions that cooperate with the mechanical system. Knowing the frequency of rotation of such rotating members is sometimes important. In mechanical systems with rotating members, rotational frequencies can be measured using tachometers or other such rotation sensors. These rotation sensors can be used in conjunction with accelerometers for diagnostic purposes, for example.
Using such rotation sensors, however, increases complexity, weight and/or cost of such systems. Additionally, the installation of tachometers and/or rotation sensors can limit mechanical designs and can require retrofitting existing mechanical systems if rotational frequency measurement is required.
It may be impractical to incorporate tachometers or other rotation sensors into certain mechanical systems. Some rotating members, for example may operate in a high temperature environment in which electro-mechanical sensors cannot survive. Some rotating members may be designed to operate in close confines that leave little room for addition of electro-mechanical sensors. Some rotating members may operate in caustic or otherwise harsh environments that may prohibit the inclusion of electro-mechanical sensors.